Great question guys. This was kind of a 2 part thread. 1 being the OP's 375 in question, which is a put together rifle. This is so obvious to a well educated Winchester model 70 guru. To the untrained eye it looks like a nice 375. The second part of this thread involves this post and this is where your question comes into play about rarity:
This rifle in question is extremely rare. According to Rule, he thought there were only 10 that were built. However, he didn't know everything about model 70's and what went out the back door with it's employees
. Back to the rifle in question. It is a 375 H&H with a standard wt barrel, which basically means it had a very light barrel on it in comparison to the other 2 configurations (24" heavy weight and 25" tapered medium wt) offered.